Bisulfate – cluster based atmospheric pressure chemical ionization mass spectrometer for high-sensitivity ( 100 ppqV) detection of atmospheric dimethyl amine: proof-of-concept and first ambient data from boreal forest

摘要

Atmospheric amines may play a crucial role in formation of new aerosolparticles via nucleation with sulfuric acid. Recent studies have revealedthat concentrations below 1 pptV can significantly promote nucleation ofsulfuric acid particles. While sulfuric acid detection is relativelystraightforward, no amine measurements to date have been able to reach thecritical sub-pptV concentration range and atmospheric amine concentrationsare in general poorly characterized. In this work we present aproof-of-concept of an instrument capable of detecting dimethyl amine (DMA)with concentrations even down to 70 ppqV (parts per quadrillion, 0.07 pptV)for a 15 min integration time. Detection of ammonia and amines other thandimethyl amine is discussed. We also report results from the first ambientmeasurements performed in spring 2013 at a boreal forest site. While minutesignals above the signal-to-noise ratio that could be attributed totrimethyl or propyl amine were observed, DMA concentration never exceededthe detection threshold of ambient measurements (150 ppqV), therebyquestioning, though not excluding, the role of DMA in nucleation at thislocation.